1. Field of the Invention
The present invention relates to C-frame press structure, and particularly, to platen designs for a C-frame press.
2. Desciption of Related Art
As shown in FIGS. 1 and 2, the typical structure of a C-frame press mainly consists of two platens 1 and 2, each including a platen column 1a and 2a; a tie-rod 3 having a nut 3a, 3b threaded at one or both ends; a compression column 4 and a back column 5. All parts are tightened together by the tie rod 3 and nuts 3a, 3b with a pre-load. In operation, an additional tension load is added to the tie-rod 3. The platen 1 of FIG. 1 includes a platen column 1a as well as a platen web 1b and a lateral stiffener 1c. 
In the illustrated conventional design, the fatigue strength of the tie-rod 3 that is subject to the alternating load often controls the press design.
It is known that the higher the compression column stiffness and/or the lower the tie-rod stiffness, the better the fatigue strength of the tie-rod.
As shown in FIGS. 3 and 4, the conventional platen design includes a platen column that is stiffened by the platen web 1b and a lateral stiffener 1c. The platen 1 has a base portion 1d for engaging a workpiece (not shown) along the lower planar surface. With the design of FIGS. 1–4, the platen column 1a, 2a is partially in series-connection with the compression column 4 and, consequently, the equivalent stiffness of the compression column 4 is reduced. In other words, the platen-column stiffness is detrimental to the tie rod 3 in the conventional design. Thus, the conventional thinking leads one of skill in the art to believe that it is undesirable to have low platen-column stiffness, and one of skill in the art would provide increased platen-column thickness.
Thus, the typical structure of a C-frame press mainly consists of two platens, a tie rod threaded at one or both ends, a compression column and a back column. All of the parts are tightened together by the tie rod with a pre-load. The conventional platen design includes a platen column that is stiffened by platen webs and lateral stiffener webs. The platen column is partially connected in series to the compression column, and consequently, the equivalent stiffness of the compression column is reduced. With this design, the platen column stiffness is always detrimental to the tie rod.
The need exists for an improved C-frame press having a platen assembly that improves the fatigue strength of the tie rod.